This is a little off topic, but you got me curious so I walked around after work today running a few very simple non-scientific tests with a variety of computers and a stopwatch to see how things look in my corner of the real world.
The following are all on exactly the same fast network (10MBit feed from a fat university pipe, low latency all around) during a low-traffic period.
My randomly-selected test sites (typed in exactly as shown) were abc.com (embedded video, redirects to abc.go.com, so that's an additional layer of speed hit), cnn.com (relatively complex but media light), MacNN.com (same), and cbsnews.com (a whole mess of embedded flash, video, and other junk). Cleared all browser caches, and in most cases the sites had never been visited anyway.
Results (times in seconds until all loading/drawing activity stops for sites in order listed above):
G4 800 (QS), 384MB RAM, 10.4.2
Safari 2.0.1: 5.0, 6.2, 6.5, [froze]
Firefox 1.0.6: 5.8, 6.0, 6.7, 15 (? - visually seemed to be finished much sooner)
Opera 8.5: 4.2, 8.0, 8.8, 5.4
G5 1.6 (iMac), 512MB RAM, 10.3.8
Safari 1.3.1: 3.4, 6.7, 7.1 (different ads?), 6.6
Firefox 1.0.6: 5.4, 5.0, 5.6, 4.3
Opera 8.5: 7.6, 8.6, 4.3, 5.1
Camino 0.8.4: 5.0, 2.0(?), 4.8, 4.0
Pentium III 866 (Micron), 384MB RAM, W2K Pro SP4
Firefox 1.0.6: 10.0, 6.9, 6.0, 17.1
IE 6: 4.2, 6.6, 5.5, 10.0 (seemed to be finished sooner)
Pentium4 3GHz (IBM), 512MB RAM, XP Pro SP2
Opera 8.5: 2.0, 6.0, 4.4, 3.6
IE 6: 11.0, 4.2, 5.2, 6.6
I also ran through the sites at home on my DP G5 2.0, 2.5GB RAM, on a slower 3MBit DSL connection, and the times came out on the low end of the above.
That's a lot of numbers, but basically it's a wash; a similarly equipped 800MHz-ish Wintel box and G4 Mac perform similarly, a similarly equipped G5 iMac and 3GHz P4 box also perform similarly except that Opera seems to be somewhat faster on Windows (and also generally bests IE), and no browser seems to make a huge difference across the board, though some did better on certain sites than others. I also re-ran a few tests, and there was some variability (whether due to network traffic, different random ads, or dumb luck I don't know).
It's also worth noting that in all but two cases the sites were mostly loaded and readable within a second or two, so there was no sense of "slowness" anywhere. The two exceptions were a roughly 1 second initial delay loading MacNN on pretty much every browser while some sort of slow response happened, and IE on windows for some reason took a long time to start displaying CNN.com--it displayed the banner, then paused noticably before drawing the rest of the page, while every other browser pretty much had it up immediately.
Make of all this what you will, but it sounds to me like it's something to do with the way your Mac is integrated with your network, not a RAMDisk.
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